The sports channel of state-owned CNTV cited Li's agency, IMG, as saying the tennis star would hold a briefing on Sunday to announce the news but also said she might make an official announcement on Friday via social media.

A separate report by CCTV-5, the sports channel of state broadcaster China Central Television, quoted unnamed insiders as saying Li, 32, will announce her retirement because of injuries on Friday.

"According to insiders, Li Na will officially announce her retirement on September 19," CCTV-5 said on its verified microblog.

"She is reportedly retiring because she is unable to continue competing due to her physical condition," it said.

The broadcaster did not give any details about its sources. An employee at the Beijing office of IMG told AFP that Li's manager was in a meeting and unable to confirm.

The world number six won the Australian Open in January but her season has been troubled by injury and she has been sidelined since late July with a knee problem.

She was ranked a career-high second in the world after January's Grand Slam win, but has slid down to sixth after missing a string of tournaments including the US Open. In July, Li also split with her influential coach Carlos Rodriguez.

She initially planned to return at the inaugural WTA Wuhan Open, in her home city, which begins Sunday.

The Beijing News reported that Wuhan Open officials had received a confirmation letter from Li dropping out of the tournament.

Organisers however told AFP no letter was received and to their knowledge Li was still playing.

A press conference has been arranged for Sunday in Wuhan, AFP understands.

Li originally played badminton after being encouraged in the sport by her father who played professionally. However, she switched to tennis after being convinced by her childhood coach.

She took a break in her career early on to study journalism at university only to return to tennis.

Li became a sporting pioneer in China when she decided to break from the state sports system in 2008 with a group of upcoming players, in a move dubbed by local media "fly alone".

The move meant that Li was able to choose her own coaches and keep most of her winnings rather than give them to the government.

The aggressive baseliner has since became one of the region's biggest stars when she won the 2011 French Open, becoming the first Asian national to win a Grand Slam singles title.

She has become a poster girl for the Women's Tennis Association (WTA), which has made a concerted push into Asia by organising several new tournaments including Wuhan.

Li previously said she considered retiring last year after a dip in form, but following encouragement from Rodriguez, she returned stronger to claim her second Grand Slam.

Her agent was forced deny fresh retirement rumours over the summer after a US broadcaster claimed she would call it a day after the China Open in Beijing, which follows the Wuhan tournament.

In an interview last month, tennis great Martina Navratilova cited Li's ability to withstand injuries as the critical question facing her as she approaches her 33rd birthday in February.

"The body is the biggest issue for her, clearly, now," Navratilova told AFP, describing Li's future as "up in the air".

While the details of Li's plans remain unclear, a potential announcement in Wuhan would mirror the retirement of China's other global sports star, basketball player Yao Ming.

The former NBA player returned to his home city of Shanghai to announce his retirement in 2011.